1. Field of Invention
The present invention relates to an electrode assembly that performs the dual functions of solution measurements and after-measurement self-cleaning.
2. Related Art
Many solution analytical processes use metal electrodes for collecting important analytical signals, such as current density, electropotential, and pH value, from sample solutions for determining the specific types and concentrations of components in such sample solutions.
For example, a potentiometric titration of a reduction-oxidation species in a sample solution relies on measuring a characteristic oxidation-reduction-potential (ORP) of such sample solution that is indicative of a titration endpoint, by using an ORP electrode comprising platinum or platinum alloys.
However, extended use of the metal electrode will render such electrode passivated (i.e., delayed and reduced response to changes in the sample solution) after repeated signal collection cycles, due to formation of solid or liquid residues on a surface of such electrode in contact with the sample solution. This is especially true in cases where an indicator electrode is used in precipitation titration analysis (e.g., titrations with silver nitrate).
Conventional methods for cleaning or reactivating the passivated electrode require disassembling and reassembling of the analytical cell that contains such electrode, which results in long off-time and is both time and labor consuming. Moreover, incorrect reassembling of the analytical cell may lead to subsequent system failure.
It is therefore an object of the present invention to provide a faster and easier method for rejuvenating the passivated electrode.
Other objects and advantages will be more fully apparent form the ensuing disclosure and appended claims.
The present invention provides an electrode assembly, which is capable of automated, in-line self-cleaning, without having to disassemble and reassemble the whole analytical cell, and therefore solving the above-described problems associated with conventional electrode cleaning methods.
The present invention in a specific aspect relates to an electrode assembly for collecting analytical signals from a sample solution, comprising:
(a) a central electrode;
(b) a measurement circuit;
(c) an auxiliary electrode; and
(d) an auxiliary current source,
wherein the central electrode is detachably connected to the measurement circuit during a measurement period, for collecting analytical signals from the sample solution, and wherein the central and auxiliary electrodes are detachably connected to the auxiliary current source during a cleaning period, to generate gas for in-line cleaning of such electrode assembly.
The central and auxiliary electrodes preferably comprise metal or metal alloys, such as platinum, stainless steel, copper, aluminum, gold, silver, etc., and alloys thereof. However, such central and auxiliary electrodes are not limited thereby in any manner, and they can also comprise carbon, glass, ceramic, and any other metal and/or non-metal materials suitable for manufacturing electrodes, depending on the specific uses they are intended for. For example, when the electrodes are used for measuring oxidation-reduction-potential in a sample solution, together with a suitable reference electrode, or when the electrodes are used for measuring in an amperometric technique where they are polarized by applying an electric potential or current in a sample solution, such electrodes preferably comprise platinum or platinum alloys.
In order to maximize the electrolytic gas generation, such central and auxiliary electrodes are immersed in a conductive electrolytic solution, preferably an acid solution, and the auxiliary current source passes electrical current between the central and auxiliary electrodes through the conductive electrolytic solution, to generate gas bubbles in a manner that is sufficient to peel away any solid or liquid residues or deposits on the central electrode and to reactively clean such central electrode.
Another aspect of the present invention relates to a method for rejuvenating a passivated measurement electrode, by using an electrode assembly described hereinabove.
Additional aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.